Continuous production of peroxidase, esterase, alkaline phosphatase and lysozyme by clones of promyelocytes

Abstract

THE classic description of maturation of cells of the bone marrow myeloid series is based on static observation of morphological and biochemical differences between cells in close proximity¹. It is generally accepted that multipotential stem cells progress under appropriate leukopoietic stimuli to myeloblasts, and then to promyelocytes, myelocytes, metamyelocytes and at least three specific mature populations with distinct biological functions: polymorphonuclear neutrophils, basophils and eosinophils¹. The stage at which a cell becomes committed to a specific population is unknown. One approach to defining the maturation relationship between myeloid cells has been through study of the production of enzymes^2–4, chemical mediators⁵ and other intra-cellular or surface proteins^6–9 specific to each leukocyte population. Histochemical techniques for identification of myeloid enzyme production have been used to correlate the production of these proteins with different stages of morphological maturation¹⁰. The inability to establish tissue culture lines derived from single myeloid cells stably arrested in development has prevented study of the degree of differentiation of cells in each stage of maturation. We report here the establishment of multiple clones of rat myeloid cells which maintain stable promyelocyte morphology in vitro and produce four enzymes. Clones derived from more primitive myeloblast cells produce only lysozyme.